1. Field of the Invention
The present invention relates to a graphene shell and a process of preparing the same, and more particularly, to a process of economically preparing a graphene shell which can have various three-dimensional configurations and a graphene shell prepared by the process.
2. Description of the Related Art
Graphite is a stack of two-dimensional sheets formed from a planar array of carbon atoms bonded into hexagonal structures. The individual sheets, referred to as graphene, can have properties different from those of graphite. Recently, as a result of testing properties of single-layered or several-layered graphene sheets, their beneficial properties have been revealed.
A noticeable beneficial property of graphene is that electrons flow in a graphene sheet as if they are weightless, which means that electrons flow at the velocity of light in a vacuum. In addition, an unusual half-integer quantum hall effect for both electrons and holes is observed in the graphene sheet.
The electron mobility of known graphene sheets is from about 20,000 to 50,000 cm2/Vs. Also, it is advantageous to use graphene sheets since products made from graphite are inexpensive while products made from carbon nanotubes which are similar to graphene sheets are expensive due to low yields obtained during synthesis and purification processes even though the carbon nanotubes are inexpensive themselves. Single wall carbon nanotubes exhibit different metallic and semiconducting characteristics according to their chirality and diameter. Furthermore, single wall carbon nanotubes having identical semiconducting characteristics have different energy band gaps depending on their chirality and diameter. Thus, single wall carbon nanotubes must be separated from each other in order to obtain desired semiconducting or metallic characteristics. However, separating single wall carbon nanotubes is not a simple process.
It is advantageous to use graphene sheets as an alternative to single wall carbon nanotubes since a device can be easily designed to exhibit desired electrical characteristics by arranging the crystalline orientation in a desired direction since electrical characteristics of a graphene sheet are changed according to the crystalline orientation. The characteristics of the graphene sheet can be efficiently applied to carbonaceous electrical devices or carbonaceous electromagnetic devices in the future.
However, although the graphene sheet possesses such advantageous characteristics, a method of economically and reproducibly preparing a large-area graphene sheet has not yet been developed. Methods of preparing a graphene sheet are classified into a micromechanical method and a SiC thermal decomposition. According to the micromechanical method, a graphene sheet separated from graphite can be prepared on the surface of a SCOTCH™ tape (available from 3M Corporation) by attaching the tape to a graphite sample and detaching the tape. In this case, the separated graphene sheet does not include a uniform number of layers, and does not have a uniform shape of ripped portions. Furthermore, a large-area graphene sheet cannot be prepared.
In another method using silicon carbide (SiC) thermal decomposition, a SiC single crystal is heated to remove Si by decomposition of the SiC on the surface thereof, and then residual carbon C forms a graphene sheet. However, the SiC single crystal as the starting material in the SiC thermal decomposition is very expensive, and a large-area graphene sheet cannot be easily prepared.
Therefore, no simple method has yet been developed to prepare a two-dimensional graphene sheet as described above, and a method for preparing a three-dimensional graphene by bending a graphene sheet is also not known in the art.